<template>
  <div class="todo-footer">
    <label>
      <input type="checkbox"  v-model="isAllChecked"/>
    </label>
    <span>
      <span>已完成{{ todoNum }}</span> / 全部{{ todoList.length }}
    </span>
    <button class="btn btn-danger" @click="removeAllDone">
      清除已完成任务
    </button>
  </div>
</template>

<script>
export default {
  name: "Footer",
  props: ["todoList", "changeAllDone", "removeAllDone"],

  // 计算属性将被混入到Vue实例中，所有getter和setter的this上下文自动绑定为Vue实例
  computed: {
    todoNum() {
      // 使用reduce作为累加器，如果选中复选框，就让它相加，否则返回当前复选框已选中的个数
      return this.todoList.reduce((p, c) => {
        if (c.done) {
          p++;
        }
        return p;
      }, 0);
    },
    isAllChecked: {
      get() {
        return this.todoNum === this.todoList.length && this.todoList.length;
      },
      set(newVal) {
        this.changeAllDone(newVal);
      },
    },
  },
};
</script>

<style>
/*footer*/
.todo-footer {
  height: 40px;
  line-height: 40px;
  padding-left: 6px;
  margin-top: 5px;
}

.todo-footer label {
  display: inline-block;
  margin-right: 20px;
  cursor: pointer;
}

.todo-footer label input {
  position: relative;
  top: -1px;
  vertical-align: middle;
  margin-right: 5px;
}

.todo-footer button {
  float: right;
  margin-top: 5px;
}
</style>
